In the production of small geometry semiconductor devices there is a need for high dielectric constant materials for use in charge storage device applications. Among the dielectric materials most commonly used for such applications are silicon dioxide, silicon nitride or a combination thereof. Other dielectric materials have also been used to make thin film capacitors. These include thermally grown silicon nitride and transition metal oxides such as tantalum oxide (Ta.sub.2 O.sub.5) and hafnium oxide (HfO.sub.2). However, it has been found that a thin film of thermally grown nitride is difficult to prepare at temperatures below 1050.degree. C. and requires a very low dew point nitrogen furnace atmosphere. Otherwise it will form a thermal oxynitride which has an even lower dielectric constant than a nitride. Silicon nitride can be formed through Chemical Vapor Deposition (CVD) but it will need an underlying thermal oxide to minimize the current leakage, because a thin silicon nitride layer formed through CVD is generally a leaky dielectric. The transition metal oxides are difficult to prepare sufficiently thin to provide the desired combination of properties such as high capacitance, low current leakage, substantial voltage breakdown strength and they are generally not stable enough at high temperatures.
The process disclosed and claimed in copending patent application Ser. No. 387,315 teaches how to make an insulating material having a substantially higher dielectric constant than that of SiO.sub.2 and Si.sub.3 N.sub.4 and low current leakage characteristics. It is also stable within a wide range of temperatures, i.e., between about -150.degree. C. and +1,300.degree. C. This accomplished through the oxidation, at above 400.degree. C., of a transition metal --silicon alloy having 40% to 90% by atomic volume of the transition metal. For example, oxidizing a layer of tantalum silicide at 400.degree. C. or higher for a sufficient period of time results in a mixture of tantalum oxide (Ta.sub.2 O.sub.5) and silicon dioxide (SiO.sub.2). We believe that the invention disclosed in the aforementioned patent application represents truly significant advances in the art as explained in detail in said application. Our present invention extends the developments in this area of technology and has the further advantage of providing materials having an even higher dielectric constant than the previously known materials.